Archives > February 2017

About two or three years ago, I spotted the largest number of snowy owls I had ever seen in southern Alberta. I haven’t seen as many this winter season, and began to wonder if there was a reason for this. Maybe I have been spending less time out of the city this winter, I’m getting rusty at spotting them or maybe there is some other driving force that influences the snowy owl population size.

As an environmental scientist, I am familiar with the snowshoe hare-lynx population cycle so I did a little research to see if there was a similar population cycle with the snowy owl and one of their prey species.

The way the snowshoe hare-lynx population cycle works is like this:

The hare population size increases when the population size of their predator—the lynx—is low.

As the hare population continues to increase due to predation by lynx being low, the lynx population begins to increase due to the abundance of preferred food, the snowshoe hare.

The snowshoe hare population eventually declines due to heavy predation brought on by the booming lynx population.

The lynx population follows the declining snowshoe hare trend shortly after with their own decline due to less available food.

The cycle continues like this, with booms and busts for each species (Northwest Territories Environment and Natural Resources). Of course, there are more factors that can come into play, but that is a simplified version.

With the snowy owl, there has been speculation and several recent studies on the relation between the snowy owl and lemming populations (Fears 2014; Smith 2014). Lemmings are small rodents that are related to voles and inhabit northern Canada. They reproduce quickly and reach peak population sizes every three to five years (Canadian Encyclopedia 2017).

There are two popular theories that explain lemming population cycles (Smith 2014):

Predators, such as the snowy owl drive lemming population cycles.

Lemmings drive their own population declines through over-population and overgrazing, which can lead to large scale die-offs.

In the summer of 2013, there was an abundance of lemmings in northern Canada. This resulted in high reproductive success rates for snowy owls and an abundance of snowy owl fledglings successfully leaving their nests. Because there were so many new owls the following winter season during their migration south, many of the young owls distributed themselves further south and closer together than normal (Fears 2014; Smith 2014). This is what lead to me seeing more snowy owls than ever before!

Lemming population booms have virtually stopped in Greenland and the Scandinavian Arctic (Fears 2014). Global warming is causing decreases in snow cover and changes in snow texture (IPCC 2014), which is believed to be causing the change in lemming population booms. Arctic Canada has also seen a trend of decreasing snow cover and increases in permafrost and surface temperatures (IPCC 2014). As trends continue in this direction, they will not favor the lemming and I speculate that we can expect to see population booms of the snowy owl become fewer and farther between.

Imagine the tallest human being in history, Robert Pershing Wadlow who was 2.47 meters tall. Now imagine a grizzly bear standing on his hind legs. Who do you think is taller? You may be surprised to find out that these behemoth bears can be over three meters tall when standing. Now how much would you suppose a 3-meter-tall grizzly weighs? What if I said over 325 kilograms! Does that sound crazy? Also, do not go thinking that you can outrun them either, since grizzlies can reach speeds of up to fifty-five kilometers per hour, and are excellent swimmers too!

Roughly, 50,000 years ago these magnificent beasts traversed the Bering land bridge making the journey from Eurasia to North America. Due to their travel itch, these bears have become the most widespread species in the entire world; however, we did not know this for some period. In fact, in the 19th century people thought there were 86 different species of grizzly! It was not until 1953 that we discovered that despite being geographically isolated and having different coat colours and sizes, that these were all in fact one species known as the brown bear, Ursus arctos. One particular subspecies the grizzly, Ursus arctos horribilis, is a little bit more aggressive then the rest. You can tell grizzlies apart from the tamer black bear – which is sometimes brown especially in open, sunny areas – by the grizzly’s dished face, and by their large muscular shoulder hump that is used for digging dens. Grizzly bear tracks are also different from that of black bears due to their longer claws.

Grizzlies may be more aggressive compared with other brown bear subspecies due to their history on the prairies. With a lack of shelter, grizzlies became accustomed to standing their ground, and naturally had to defend themselves instead of hiding.

The population in Canada has dwindled down to 20,000, being mostly located in British Columbia, but also throughout the Alberta Rockies, Yukon, Northwest Territories, and Nunavut. Historically, in Alberta, grizzly population levels were at 6,000-9,000 bears. In 2002, their numbers dropped to around 1,000, and in 2006 there was a hunting ban, but it was not until their population fell to 691 in 2010 that they became listed as a threatened species in Alberta. Presently in Alberta, you will find them in the Banff and Jasper National parks, as well as on the foothills along the mountains, and in the northwest boreal forest.

The biggest hurdle towards achieving a sustainable grizzly population is habitat fragmentation. When grizzly populations become isolated and fragmented they become susceptible to local extinction due to inbreeding, disease, fire, and human induced mortality. Many of these sub populations of grizzly are going extinct and one of the main causes of fragmentation are roads. Some reasons roads cause bear deaths are because of vehicle collisions and poaching. Also, female grizzlies are reluctant to cross roads, which reduces their ability to breed and to gather resources for winter. Typical female ranges are 150 – 3,000 km2 and so a reduced range may prevent her from gathering enough fat before winter. If she does manage to survive, less weight means that fewer cubs will be born.

So you may be asking yourself now, “What can I do to protect this iconic species?” Well for starters, always make sure to properly dispose of your trash and waste on campgrounds. Make sure to scare off grizzlies if you see one by making lots of noise. Try to avoid encounters as much as possible, by avoiding smaller trails, industrial access roads, and areas with lots of berries in the fall. Make sure you report bear sightings to your local authority to prevent conflicts with humans and watch out for bears on the road!

Similar to a keystone which provides the stability to an archway, a keystone species helps provide stability to the surrounding ecosystem. Most animals play a vital role in the well-being of their local environments and the other species that inhabit them, but some deliver more critical services that are essential to maintaining balance. Some animals build new nests or burrows year after year while other animals borrow these discarded homes and would be without shelter if this keystone species was lost.

Pollinators like bumblebees, butterflies, and hummingbirds help sustain the next generation of plants by cross-fertilizing which produces fruits, seeds and vegetables for other animals to eat. Predators like wasps, wolves and cougars help prevent herbivores like beetles, rabbits and deer from over-eating those plants so that they can be pollinated again in future seasons.

Keystone species may also sustain the soil and water quality. Wolves may prey on deer which prevents the deer from eating too many saplings in a given area. This allows shoots to develop into large trees, whose root systems prevent erosion and support river banks. The rivers can then maintain adequate depths, turbidity, nutrient levels and temperatures to support fish and other aquatic plants and animals.

Alberta is home to a number of keystone species. These include beavers whose dams create ecosystems for many other animals like moose and ducks, Richardson’s ground squirrels whose underground tunneling aerates the soil to support native grasses while also providing shelter to other animals and grey wolves who help to maintain a healthy population of ungulates. Without these important species, ecosystems may become imbalanced which in turn could lead to an increase in the number of displaced wildlife that end up in conflict with humans and who ultimately find their way into AIWC’s care.

Running across electrical wires, up trees and across roads, you’re probably pretty familiar with Sciuridae. Wait a second, what is that? Let me tell you!

Sciuridae is the animal family that includes tree squirrels, ground squirrels, flying squirrels, marmots, prairie dogs, chipmunks and more.

Around Alberta, you probably see one of these bushy-tailed species (the red squirrel) on a regular basis.

These furry friends are most recognisable by their tails, which make up almost half their length! Squirrels use their tails for balance as they jump from tree to tree or rooftop to rooftop. They are agile, aren’t they? It seems like squirrels are everywhere in Alberta!

Their natural habitat is in Alberta’s boreal, coniferous or mixed forests. But squirrels seem comfortable living just about anywhere.

A squirrel’s diet consists mainly of seeds and nuts, and they have a special place in their hearts for pinecones and spruce tree droppings!

Did you know that squirrels might also eat things like bird’s eggs, flowers, fruits, mushrooms and more? They are savvy little rodents who get by on what they can.

Unlike other types of squirrels, red squirrels don’t bother with hibernating through the winter. They aren’t scared of a little cold weather! Red squirrels stay active throughout the winter by collecting nuts and climbing trees just like they do the rest of the year!

Red squirrels start breeding in March or April, giving birth to four or five pups a couple of months later. Babies are usually born in the cavities of trees or in nests built into branches.

Tip: Trying to figure out if squirrels are around? Look for piles of cones or discarded shells from previous nut meals.

Another common Sciuridae is the Red-tailed Chipmunk. These small rodents are only about 21 to 25 cm long and just like squirrels, their tails make up roughly half of their total body length.

Chipmunks are reddish in colour and have bright orange or rust colours under their tails. They have signature stripes in black or brown and light tawny or creamy white.

Alberta chipmunks tend to dwell in conifer forests in the subalpine regions of Waterton Lakes National Park and the West Castle Valley.

Chipmunks enjoy munching on seeds from saskatoon, wild rose and snowbrush bushes. They eat leaves, flowers and fruits from these plants.

Unlike their squirrel cousins, chipmunks tend to spend winter alone in their burrows. But don’t feel bad for the little critters; come spring, female chipmunks use their burrows as nurseries for litters of two to four young.

Keep an eye out for these little rodents. Alberta is full of diverse, beautiful wildlife, and you don’t even need to look further than the electrical poles outside your house to find them!

By Nina Grossman, AIWC Volunteer

“Each species is a masterpiece, a creation assembled with extreme care and genius.” Edward O. Wilson